The present disclosure relates generally to welding systems and, more particularly, to welding torches having wire feed systems that include piezoelectric mechanisms, such as piezoelectric walk motors and piezoelectric worm drives.
A wide range of welding systems and welding control regimes have been implemented for various purposes. In continuous welding processes with consumable electrode, gas metal arc welding (GMAW), and more specifically, metal inert gas (MIG) or metal active gas (MAG) techniques (collectively called GMAW) allow for formation of a continuing weld bead by feeding welding wire electrode from a welding torch (welding torch). Electrical power is applied to the welding wire, and a circuit is completed through the workpiece to sustain an arc that melts the welding wire and the workpiece to form a desired weld. Another consumable electrode arc welding process is submerged arc welding (SAW), in which the arc is buried under a bed of flux. A wire consumable can be fed into a GMAW or SAW melt puddle, or into a puddle created by non-consumable electrode processes such as gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, plasma arc, laser, electron beam, and so forth, where filler wire is added to the melt pool for welding, cladding, overlaying, hardfacing, and brazing. The added wire can be “cold” or as received (e.g., known as “cold wire”), or preheated resistively or inductively (e.g., known as “hot wire”). The embodiments described herein apply to all the aforementioned processes where wire is used as a consumable, thus the word “welding”, as used herein, is hereby defined to include these processes for the purpose of the present disclosure.
Advanced forms of welding with consumable electrode can be based upon controlled short circuits between the welding wire and the advancing weld puddle formed from melted metal of the workpieces and the welding wire. One method of controlling short circuit behavior is welding current reduction during short-to-arc and arc-to-short transitions via current regulation or a secondary switch in the welding power supply.
In other applications, the controlled short circuits may be created by a reciprocating wire feed system configured to oscillating the welding wire in and out of the advancing weld puddle. By oscillating the welding wire in and out of the weld puddle, liquid at the end of the welding wire may be dipped into the puddle mechanically and detached from the welding wire when the wire is pulled out of the puddle, thereby accomplishing a “controlled short circuit” effect. In addition to controlled short circuit in consumable electrode arc welding, reciprocating wire feed is also useful in non-consumable electrode arc welding with filler metal, such as hot wire or cold wire TIG, where the welding wire is oscillated by reciprocating wire feed and fed into a melt puddle created by non-consumable TIG arc. Typically, mechanical motion of the wire is slow. To achieve desired higher deposition and faster welding travel speed, the wire must move bidirectionally in excess of 1000 inches per minute and at a rate in excess of 100 Hz at 100% duty cycle. Traditional reciprocating wire feed systems use bidirectional motors, which typically have relatively high torque requirements to overcome the inertia of the motor, the drive rolls and/or gears. In addition, bidirectional motors may have limitations on the reciprocating frequency (which in turn imposes limitations on wire feed and travel speeds and productivity), and may be susceptible to overheating, and/or may be oversized, which may cause weld joint accessibility issues.